In network management, an event is something that happens about which a manager (network, system, or application manager) needs to know. A notification is a method by which information about an event is passed to the manager. A notification is an unsolicited message, for example, one that is delivered to a server from an agent that is monitoring a networked device. The notification typically carries information that human network administrators have designated as useful, such as descriptions of a problem, an unusual condition, or an important change of state (for instance, a successful reboot). Network devices are often configured to monitor their environments for such conditions and to report them to a server automatically.
SNMP (Simple Network Management Protocol) defines traps as a type of notification. A trap is sent using the UDP network protocol. Routers, switches, and devices running monitoring agents are examples of network entities that send traps to a NMS.
SNMP versions 1 and 2 (or v1 and v2) have different definitions for traps. Version 1 defines a trap PDU (protocol data unit, which is the collection of data transmitted as a single message) to have a generic trap type, a specific trap type, an enterprise value, and a collection (possibly empty) of variable bindings. Generic trap type includes enumerated values such as coldStart(0), warmStart(1), linkDown(2), linkUp(3), authenticationFailure(4), egpNeighborLoss(5), and enterpriseSpecific(6). Specific trap type gives a type number for enterprise-specific traps. Enterprise is an OID (object identifier) specifying the vendor that defined the specific trap. Variable bindings are use-specific OID/value pairs. SNMP v1 includes a syntax for defining variable bindings.
SNMP version 2 defines a trap PDU to have a notification OID and a collection of variable bindings. The notification OID provides in a single property information that the SNMP v1 provided in the fields for generic-type, specific-type, and enterprise. SNMP v2 variable bindings have conventional structures for the first two bindings. The first binding is sysUpTime, which indicates how long the described system has been operating. The second binding is snmpTrapOid (identification), which identifies the particular PDU. Any additional SNMP v2 variable bindings are use-specific.
Each trap has its own particular definition within the scope laid out by SNMP. The definition is provided in a MIB (management information base) document. A v1 or v2 trap PDU includes information that identifies its defining MIB.
Temporal duplication occurs in the stream of traps arriving at a given server when multiple traps in the stream are carrying substantially the same information (for example, describing the same network condition) at roughly the same time.